The JSON data format uses the field name string as the attribute name, you can use a "naming" parameter to specify that you would like to use field id as the attribute name to identify a field.
Possible values include: EID (Field Id), FNAME (Field Name).
curl --get -d "naming=EID" \ -H "Authorization:Basic YOUR_API_KEY_GOES_HERE" \ -d api \ https://www.ragic.com/demo/sales/1
